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    <script>
        // 1.声明一个变量age
        var age;
        // 2.给变量赋值
        age = 21;
        // 3.输出变量
        console.log(age);
        // 4.变量的初始化
        var myname = '朝歌阿';
        console.log(myname);
    </script>
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